This research project will demonstrate proof of principle, safety and determine the optimal methylene blue (MB)/EDTA drug and light parameters necessary for chronic recurrent sinusitis (CRS) treatment in an in vitro novel anatomically accurate human maxillary sinus CRS polymicrobial biofilm model and in an ex vivo live human respiratory ciliated mucosa model. These results along with our already developed disposable sinus illumination system will be immediately translatable to a human clinical trial for CRS treatment and may result in the rapid adoption and commercialization of this much needed therapy. CRS is one of the most common chronic conditions in the United States affecting an estimated 37 million Americans. It is also estimated that CRS results in 18-22 million office visits per year and over 500,000 emergency visits per year resulting in an estimated 73 million restricted activity days with an aggregated cost of six billion dollars annually. In clinical practice there is a significant subpopulation of patients with CRS who remain resistant to cure despite endoscopic sinus surgery, allergy therapy and culture directed long term oral, topical or intravenous antibiotic therapy. Numerous studies have reported the presence of antibiotic resistant Pseudomonas aerugenosa, Hemophilus influenza, Streptococcus pneumoniae and Staphylococcus aureus biofilms in the sinuses of cure resistant CRS. Microbial biofilms, including CRS biofilms, are notoriously resistant to standard antibiotic therapy as well as host immunologic defense mechanisms therefore contributing to the dismal cure rates of CRS and to increased antibiotic resistance. Due to the failure of standard therapies to control and cure CRS, there is an unmet medical need for an alternative clinically effective, non- invasive, non-toxic, cost-effective, repeatable, painless topical non-antibiotic treatment modality for CRS that does not result in antibiotic resistance. MB based antimicrobial photodynamic therapy (aPDT) has the significant potential to successfully achieve these goals with the advantages of rapid adoption of the therapy as well as rapid commercialization. This grant proposal will determine the optimal MB drug and light parameters necessary to effectively treat human CRS polymicrobial biofilms in a novel anatomically accurate maxillary sinus model. In addition, histopathological analysis will be performed on the aPDT treated live human respiratory ciliated mucosa to demonstrate the safety of aPDT on maxillary sinus mucosa. Although MB aPDT has been demonstrated to be effective in eradicating biofilms in vitro, these studies will represent the first known systematic studies of MB aPDT in an ex-vivo model, including evaluating the effectiveness of the therapy and safety of the therapy, on biofilm colonized human respiratory ciliated mucosa as is found in the human paranasal sinuses. The optimal treatment parameters determined from this study are then planned to be directly translated to a human clinical trial for the treatment of CRS. On a more global level, the benefit of a non-antibiotic therapy for infection control would be considered a revolutionary medical advancement that could be used in wide ranging medical applications and would positively affect the quality of life for millions of people worldwide. PUBLIC HEALTH RELEVANCE: Chronic recurrent sinusitis (CRS) is one of the most common diseases in the United States. It is estimated that CRS results in 18-22 million office visits per year, 73 million restricted activity days and an aggregated cost of $6 Billion annually. In clinical practice there is a significant subpopulation of patients with CRS who remain resistant to cure despite endoscopic sinus surgery, allergy therapy and culture directed long term oral, topical or intravenous antibiotic therapy. Due to the failure of standard therapies to control and cure CRS, other novel non-antibiotic therapies are desperately needed that are able to destroy or control biofilms and antibiotic resistant bacteria. Developing such a therapy is the specific objective of this research and development effort. MB based antimicrobial photodynamic therapy (aPDT) has the significant potential to successfully achieve these goals with the advantages of rapid adoption of the therapy as well as rapid commercialization. This grant proposal will determine the optimal MB drug and light parameters for safe and effective CRS treatment in an in vitro novel anatomically accurate human maxillary sinus CRS polymicrobial biofilm model and in an ex vivo live human respiratory ciliated mucosa model, the results of which will be directly translated to a human clinical trial for the treatment of CRS.